Hydraulic system for a boat drive

ABSTRACT

A hydraulic system for steering and tilting an outboard drive unit for a boat including a pump, a steering sub-system including a double acting cylinder and piston connected to provide steering movement to a steerable part of the unit and provided with hydraulic liquid from the pump, and a trimming and tilting subsystem including a cylinder and piston assembly provided with liquid from the steering sub-system. Manual valves control tilting and trim positioning of the unit, and steering, while pressure relief valves are arranged to prevent damage to the unit and system upon excess steering control, striking of external objects, and the like.

United States Patent Bergstedt [151 3,654,889 1451 Apr. 11, 1972 HYDRAULIC SYSTEM FOR A BOAT DRIVE [72] Inventor: Karl Abdon Bergstedt, Goteborg, Sweden [73] Assignee: AB Volvo Penta, Gothenburg, Sweden [22] Filed: Sept. 28, 1970 [21] Appl. No.: 75,909

[52] U5. CL ..115/35, 115/41 HT [51] Int. Cl ..'...B63h 25/42 [58] FieldoiSearch ..l15/35,4l,41l-1T, 34

[56] References Cited UNITED STATES PATENTS 3,010,424 11/1961 Peterson et al .;.115/41 R 3,285,221 11/1966 North ..ll5/4l HT Primary Examiner-Milton Buchler Assistant Examiner-Carl A. Rutledge Attorney-George H. Baldwin and Arthur G. Yeager [5 7] ABSTRACT A hydraulic system for steering and tilting an outboard drive unit for a boat including a pump, a steering sub-system including a double acting cylinder and piston connected to provide steering movement to a steerable pan of the unit and provided with hydraulic liquid from the pump, and a trimming and tilting sub-system including a cylinder and piston assembly provided with liquid from the steering sub-system. Manual valves control tilting and trim positioning of the unit, and steering, while pressure relief valves are arranged to prevent damage'to the unit and system upon excess steering control, striking of external objects, and the like.

8 Claims, 6 Drawing Figures PATENTEDAPR '11 1972 3,654,889

SHEET 1 OF 4 INVEN 70/? ffarl 4M9!) Bergyr PATENTEDAPR 11 I972 3,654, 889

SHEET 3 BF 4 FIG.5

lNl/[NTOR Karl 1461/0 Baryszedf ATTORNIV HYDRAULIC SYSTEM FOR A BOAT DRIVE It is an object of the invention to provide improved hydraulic steering and tilting and trimming arrangements for a tiltable and steerable outboard drive unit for a boat. More specific objects are to provide a hydraulic system including a single source of pressure fluid for power steering and power tilting and trimming of an outboard boat drive, and to provide self or automatic bleeding of entrapped air in such system.

Further specific objects of the inventor are to provide an improved hydraulic tilting, trimming and damping cylinder system for a boat drive unit; to provide effective compatibility between hydraulic power steering and power trimming and tilting systems, or sub-systems, for an outboard drive leg for a boat; and to provide in a hydraulic tilting and trimming system for an outboard drive leg improved controls for adjusting or setting and for maintaining the trim position of the leg, for rapidly tilting the leg, for returning the leg from tilted or rearwardly trimmed position to a forward position of minimum tilt, for locking the leg against tilting while the propeller is operated in reverse, for releasing the leg for rearward tilting upon striking a floating or submerged object and for damping the movement of the leg during such tilting and for controlling its return movement from tilted position, together with improved check and pressure relief valve arrangements for minimizing the occurrence of excess hydraulic pressures in the hydraulic system and other effects which might cause damage to the leg or hydraulic system or related components of the drive.

The invention described and claimed in this application is shown as applied to an inboard-outboard drive arrangement as described in my co-pending application Ser. No. 907, filed Jan. 6, 1970, entitled Boat Drive Arrangement and assigned to the assignee hereof. Reference is made to that application for a further description of details common to the applications.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a sectional side elevational view of a boat drive embodying certain components of the hydraulic system according to the invention;

FIG. 2 is a sectional side elevation of a tilting and trimming cylinder assembly according to the invention, shown together with representations partly broken away and in section of portions of the outboard leg and the mounting means therefore;

FIG. 3 is a sectional view on an enlarged scale of portions of the cylinder assembly taken along line 3-3 of FIG. 2;

FIG. 4 is a sectional view on an enlarged scale taken along line 44 of FIG. 1;

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4; and

FIG. 6 is a schematic diagram of the hydraulic system according to the invention.

As seen in FIG. 1, the drive includes an inboard engine 1 provided with a forward, neutral and reverse transmission operated by a lever 25 controlled by a suitable linkage 26 from the usual operation station in the boat 2. Controls for the steering and trim and tilt arrangements are also preferably operable from such station, the trim and tilt cylinder 18 being provided with a reverse lock valve having an operating lever 20 coupled by a linkage 19 to the lever 25 whereby the reverse lock valve is moved into a lock position simultaneously as the transmission is shifted into reverse.

The upper portion 13 of tiltable and steerable outboard leg or housing 12 is mounted to boat transom 3 for trim and tilt movement on a horizontal transverse tilt axis T on arms 9 (seen in FIG. 2) supportedly attached to the boat by means including a supporting bracket or shell 5, all as further described in my said copending application. Tilt cylinder 18 is pivotally mounted to bracket 5 by means of a cylindrical journal boss 110 extending from the cylinder and pivoted in a bearing block 111 integral with the bracket 5. Bumper 24 limits the forward tilt position of housing portion 13 with respect to bracket 5. Lower portion 14 of leg 12 constitutes a steerable propeller housing which mounts propeller 15. The propeller shaft 58 is driven by gears 57 and 62 from downwardly and forwardly extending driven shaft 42, and this shaft is, in turn driven by gears 39 and 40 from countershaft 32 mounted in the upper housing portion. Engine drive shaft 27 is connected through double universal joint 30, 31 to countershaft 32.

Upwardly extending neck 47 of lower housing portion 14 is rotatably supported from the upper housing portion by means of pin bearing 51 and ball bearing 52 on a steering axis coaxial with the driven shaft 42. Shaft 42 is supported in bearing 43 in the upper housing and in bearings 56 and 45 in the lower housing. The upper housing includes a chamber 77 forming a cavity 78 in which a steering rack member 55 and cooperating gear teeth 54 of the neck are disposed. The chamber is oil filled and has communication through bearing 52 into the oil filled interior of propeller housing portion 14. Oil seal 53 between circular edge portions of the upper and lower housing portions prevents escape of oil. The oil filling the chamber and the interior of the lower housing is a part of the hydraulic fluid supply for the hydraulic steering and trimming and tilting system. The oil, being under pressure, also supplies lubrication to gears 39 and 40 and to the bearings 43, 44, and 51, as well as to the bearings for countershaft 32 in the upper portion of the upper housing. A suitable oil seal 112 is provided around shaft 32 at its emergence from the upper housing.

It is preferred for properly balanced operation that two identical trimming and tilting cylinder assemblies 18 be employed, connected in parallel and disposed one on each side of the centerline of the outboard leg. Details of a cylinder assembly 18 are shown in FIG. 2. As there shown, piston 115 is disposed in a thin walled operating cylinder liner 116 which is, in turn, disposed within a relatively heavier casing cylinder 1 17 which forms end walls for the operating cylinder and from which the mounting bosses extend outwardly. The piston rod 118 extends outwardly through outer end wall 119 of the casing and is slideably sealed therethrough by packing 120. The outer end 121 of rod 118 is pivotally attached by means of a pin 122 to an integral portion 123 of upper housing portion 13, pin 122 being offset below tilt axis T established by the pivot pin 10 which mounts the upper housing portion to the boat. The cylinder assembly 18 is thus seen to span the tilt axis and, upon extension, to cause tilting, or rearward movement, of the outboard by an axis T.

As shown in FIG. 2, the diameter of piston rod 118 is substantial with respect to the internal diameter of liner 116, being preferably not less than about one-third and not more than about three-quarters of such diameter.

An oil passageway 124 communicates with the interior of liner 116 adjacent end 119 and extends outwardly of the liner within casing 117 to a valve-containing inner end assembly 125 for the cylinder. The interior of the liner 116 is connected into the inner end assembly through a passageway 126. A heavily spring loaded relief valve 127 is disposed in assembly 125 and connects passageway or conduit 124, upon the occurrence of excessive pressure therein, into conduit 126. Thus, while valve 127 is normally closed, if the cylinder assembly is forced to extend, as when the outboard leg strikes an object which forces it to tilt, hydraulic fluid may flow from conduit 124 through conduit 126 into the inner end chamber 200 of the cylinder liner. As piston 1 15 moves in a outward direction, a greater volume of liquid must enter behind the piston than is displaced ahead of it. Conduit 126 continues around ball 128 of valve 127 into conduit 129 and communicates therethrough with chamber 130 of pressure relief valve 131. The movable valve member 132 of valve 131 is more lightly loaded than ball 128 of valve 127 and member 132 raises to admit the additionally required liquid into valve chamber 130 and thence into conduit 126 from conduit 133. Conduit 133 connects with passageway 134 in the plug 141 of reverse lock valve 135 when this valve is open. As seen in FIG. 3, passageway 134 is connected through a check valve 136 to a hydraulic fluid connection 137 which, in turn, as later described, is connected to an oil sump, whereby, during normal forward operation with the reverse lock valve open, if the drive leg kicks up, hydraulic fluid from the oil sump passes through check valve 136, passageways 134 and 133, past valve member 132 into chamber 130, and through connecting conduits 129 and 126 into the inner end chamber 200 of the cylinder. At the same time, fluid is also passing out of the outer end of the cylinder through conduit 124 into passageway 134 and thence into the inner end of the cylinder.

The fluid connections 138 and 139 are provided into chamber 130, one of which, i.e. 139, is provided with a pressure fluid conduit as later described and the other 138 interconnects the chambers 130 of the identical parallel connected cylinders of the drive assembly. Fluid connection 140, in communication with conduit 124, is similarly provided to interconnect and provide free communication between the outer interior portions of the parallel connected cylinder assemblies. (The parallel connected cylinder assemblies are shown at 18 and 18 in FIG. 6).

The plug 141 of reverse lock valve 135 includes a passageway 142 which provides communication between conduit 124 and check valve 136 whether the valve is in open position connecting passageway 134 to conduit 133 or in closed position with the passageway 134 closed off from conduit 133. Plug 141 is provided with a suitable operating arm or lever 20.

The spring load on relief valve 131 is sufficient to prevent the leg from tilting or floating" up when, during forward propulsion, the throttle is abruptly moved to idle position or the gears are shifted into neutral. If the leg strikes an obstacle or is otherwise forced to tilt by some externally applied force, valve 131 opens but provides a damping force resisting such tilting. Should the reverse lock valve be closed while the boat is moving forwardly and if a floating object is then encountered, the more heavily loaded relief valve 127 will open to prevent destructive pressures in the hydraulic system or damage to the leg or mechanical parts of the drive unit.

' Normally, the reverse lock valve is closed only when the gears are in reverse drive position. During reverse drive, the leg is held against tilting movement by the heavy spring load on valve ball 128. The lighter spring loading of valve 131 is insufficient to hold the leg against tilting when the propeller is being driven with substantial power in reverse.

It will be seen in FIG. 2 that a flexible diaphragm or boot 143 seals to the mounting shell 5 outwardly around cylinder 18 to prevent the entrance of water into the boat.

The steering mechanism disposed in the outboard leg is best shown in FIGS. 4 and 5. As seen therein, the upstanding neck member 47, which is rigidly attached to lower housing 14, is provided exteriorly throughout somewhat less than half of its periphery with teeth 54 meshing with teeth 63 of rack member 55. The rack member carries a piston at each end, piston 64 being disposed in a cylinder 65 and piston 66 being disposed in a cylinder 67. The cylinders have closed outer ends 68 and 69, respectively, and are provided with suitable connections to respective hydraulic fluid lines 22 and 23, whereby the piston and cylinders constitute a double acting hydraulic cylinder and piston mechanism for moving the rack member back and forth. Supplying of fluid under pressure through line 22 causes rotation of portion 14 of the leg about the axis of shaft 42 in a direction to steer the boat toward a heading more to port. Supplying of pressure fluid through line 23 results in alteration of course toward a more starboard heading.

The hydraulic system includes a pump and control elements generally indicated at 70, the control elements being controlled by a steering wheel 71 operable to cause the flow of hydraulic fluid into conduit 22 and to permit return of fluid from conduit 23 in response to rotation of the wheel in one direction and vice versa in response to rotation in the opposite direction.

A hydraulic fluid supply or sump generally indicated at 72 is arranged to supply fluid for the system.

The rack member has motion in each direction limited when one or the other of pistons 64 and 66 meets the respective cylinder end wall 68 or 69. The teeth 63 on rack 55 extend through a distance therealong, and the teeth 54 on neck member 47 extend around the periphery thereof, sufficiently to accommodate the full extent of the pennitted movement of rack 55. For example the rack may be arranged to move sufficiently to rotate neck member 47 and lower housing 14 through a total of approximately 60, 30 on each side of the dead center or straight ahead steering position.

In the construction shown, rack member 55 is provided with a partially threaded reduced generally cylindrical end portion 73 which passes through piston 64 and onto which nut 74 is screwed up against the piston to hold the piston firmly against shoulder 75 of the rack member. The end portion 73 is longitudinally bored at 76 into a cross-bored chamber 77 in the rack member. The projection 50 constitutes a fluid containing chamber and housing for the rack and pinion mechanism and the interior 78 of the housing chamber has communication through a check valve 79 into the chamber 77 within the rack member. The check valve 79 may include a light spring 90 seated on pin 91.

The cylinder 65 tenninates at an edge 80 which, at cut-away portion 80', exposes a small part of the wall 81 of piston 64 when this piston is fully extended, that is, with piston 66 stopped by or very close to end wall 69. A port or passage 82 is drilled into this portion of the piston wall and communicates with the interior of cylinder 65 through groove 83 formed around portion 55 of the rack and through passage 84 drilled from piston face 89 to the groove.

The arrangement associated with piston 66 will be seen to be identical to that associated with piston 64 as above described, including bore 85, port 86, check valve 87 and passage 88 which correspond, respectively, to bore 76, port 82, check valve 79, and passage 84.

The above described arrangement provides for self-bleeding and air scavenging of the steering system. Hydraulic liquid supplied through line 22 into cylinder 64 causes the piston 64 to move in a direction outwardly of the cylinder until piston 66 nearly meets wall 69, whereupon port 82 is exposed to the chamber interior 78 through cut-away portion or notch 80'. Whatever air may be in line 22 and cylinder 65 now passes together with hydraulic fluid into bore 76, through passages 82 and 84 and through port 82 into the interior 78 of the housing chamber. The increasing pressure in the housing chamber opens the lightly loaded check valve 87 and first any entrapped air, and later hydraulic fluid, pass through the check valve and bore 85 into cylinder 67 and thence through line 23, finally to return to sump 72. Operation in reverse direction to supply hydraulic fluid under pressure through line 23 forces piston 66 to move in a direction outwardly of cylinder 67 until port 86 is uncovered, whereupon hydraulic fluid and any remaining trapped air pass through channels 88 and 86 into chamber 78 and thence through check valve 79 and bore 76 into cylinder 65 and through conduit 22 and finally to the sump 72. Fluid is thus circulated back and forth by turning the steering wheel to and beyond its full steering effect in one and in the other direction a sufficient number of times to insure complete bleeding or scavenging of the air from the system.

In operation, the steering wheel now controls the movement of rack 55 between full starboard and full port steering positions of the lower housing up to the point at which port 82 or port 86 is uncovered, whereafter continued movement of the wheel will force a small flow of hydraulic fluid through the chamber interior 78, as when the system is being bled. The lower housing may be turned slightly beyond the full normal port or starboard steering position by an external force until one or the other of pistons 64 or 66 meets the respective cylinder end wall 68 or 69. Such end play in the system, with properly proportioned components, will be small, such as less than one degree of swing of thelower housing. Thus port 82 should become uncovered only when piston 66 has approached very close to wall 69 at the maximum steering to port position of the piston while port 86 should become un covered at the maximum steering to starboard position.

The complete hydraulic steering and trimming and tilting system may be best understood by reference to FIG. 6. Pump 144, driven by the propulsion engine 1, or by a separate motor or other convenient means, supplies hydraulic liquid from sump 72 under pressure into line or conduit 145. The pressure is regulated by a spring loaded regulator valve 146 which returns excess liquid through oil cooler 147 and filter 148 to the sump. Conduit 149 is connected to receive pressure liquid through spring loaded check valve 150 from conduit 145 and to supply such liquid into a hydraulic hydrostatic servo control with internal follow-up shown at 151. The control includes a cylindrical housing 152, a hollow cylindrical selector valve spool or sleeve 153 rotatably disposed and fitting closely within the housing 152, and an inner cylindrical plug 154 rotatably disposed and fitting closely within sleeve 153. The control further includes metering follow-up arrangement 155 embodying inner and outer toothed ring elements 156 and 157, respectively, arranged in the manner of an orbital gear pump, the outer ring element 157 being fixed and having, for example, six inward teeth and the inner rotor element 156 having five outward teeth. If oil under pressure is introduced into the space between the inner and outer elements through oil channel 158 in partition portion 159 of casing 152, the oil passes through the metering arrangement and is supplied into oil channel 160 causing the element 156 to rotate orbitally through a number of degrees of rotation proportionate to the volume of oil passing therethrough. Oil passing through metering device 155 from oil channel 160 to channel 158 will cause rotation of element 157 in the reverse direction.

The inner, orbitally rotatable metering element 156 is coupled to rotate sleeve 153 by means such as a pin 161, which passes loosely through an opening 162 in partition 159 and an opening 163 in plug 154, and which fits in a socket 164 in sleeve 153. The fit of pin 161 in opening 162 is such as to allow, for example, or of rotational freedom between the pin and plug 154, but no appreciable rotational freedom should be allowed between the pin and sleeve 153.

With sleeve 153 and plug 154 in neutral position, a port 165 in casing 152 communicates with a channel 166 in sleeve 153, and this channel communicates into plug channel 167, whereby oil is supplied from conduit 149 into channel 167. Channel 167, in turn, is in communication with sleeve channel 168, and this channel communicates through casing port 169 into the outlet line 170 from the hydraulic steering subsystem.

It will be seen that sleeve 153 is provided with a circular groove opposite each of the ports in casing 152. For example, groove 171, with which oil channel 166 is in communication, is arranged to be in alignment with port 165 at all times, regardless of the rotative position of the sleeve in the casing. Similarly, groove 172, which also extends completely around sleeve 153, and with which oil channel 168 communicates, is at all times open to port 169.

Channel 167 has a first branch 173 which is connected to port 158 only when plug 154 is rotatably displaced with respect to sleeve 153 in one direction from the neutral position, specifically in the direction corresponding to steering to port. Channel 167 has a corresponding second branch 174 which is similarly placed in communication, through a jumper channel 175 in sleeve 153, a cross plug channel 176, and sleeve channel 177 with port 160 when plug 154 is rotatably displaced from its neutral position with respect to sleeve 153 in a direction for steering to starboard.

Port 158, upon steering to starboard is placed in communication with conduit 23, the connection being completed from this port through sleeve channel 178, cross plug channel 179, and sleeve channel 180 with port 181. At the same time, a connection is established from conduit 22 through its port 182, sleeve channels 183 and 184 and plug jumper channel 185 to outlet line 170. The connection from port 181 into outlet line 170 is closed off when the plug is in neutral position and also when it is displaced in the sleeve in the direction to steer to port because the jumper channel 186 is in communicating alignment with sleeve channels 187 and 188 only when the plug 154 is displaced in the direction for steering to starboard.

Upon turning of the steering wheel 71 in a direction to turn plug 154 for steering to port, jumper channel 189 comes into alignment with branch channel 190, which connects to port 160, and with sleeve channel 191, which communicates into port 182, thereby to permit oil to flow from the meter into conduit 22.

It will be noted that circular groove 192 formed in the end of sleeve 153 is connected to channel 177 and that similar groove 193 is connected to channel 178, whereby port is connected to channel 177 and port 158 to channel 178 regardless of the rotative position of the sleeve in casing 152.

Accordingly, with plug 154 in neutral position within sleeve 153, oil from line 149 passes through channel 166 into channel 167 and therethrough into channel 168 and into outlet line 170. Branch channels 173 and 174 are closed off at the sleeve, however, cross-plug channel 179 is closed off at the sleeve, and jumper channels 185, 186 and 189 are displaced from their corresponding sleeve channels, whereby no oil can flow in or out of conduits 22 or 23 or in or out of meter 155.

In order to efiectuate steering to port, oil is forced into conduit 22 and is at the same time permitted to flow from conduit 23 into outlet line 170. This is accomplished by turning the steering wheel 71 so as to rotate plug 154 in sleeve 153 in the direction which causes branch channel 173 to align with channel 194, thereby to cause oil under pressure to flow through port 158 into the meter, and which also causes the port 160 to be opened into channel 191 by alignment of jumper channel 189 with its associated sleeve channels 161 and 191. At the same time, jumper channel 186 aligns with its sleeve channels 187 and 188 to open conduit 23 into outlet line 170, but channel 167 remains isolated from channel 176 and is closed off from channel 168, while channels 179, 183 and 184 remain closed. The flow of oil measured through the meter causes rotor 156 now to drive sleeve 153 until the neutral relative position between plug 154 and the sleeve is reestablished. When neutral position is reached conduits 22 and 23 are closed off, locking the steering pistons in position, and oil is once again permitted to flow through channel 167 into the outlet line.

Rotation of the wheel in the opposite direction, to cause a steering movement toward starboard, results in opening of channel 174 into channel 176 and thence through channel 177 to meter port 160 and opening of channel 178 from port 158 into channels 179 and to conduit 23. At the same time jumper channel connects conduit 22 into the outlet line 170, while branch 173 remains closed off from channel 194, channel remains closed off from channel 191, channel 186 remains closed ofi from channels 187 and 188, and channel 167 is closed off from channel 168. Oil now flows from conduit 149 via channels 166, 167, 174, 175, 176 and 177 to port 160 to enter the meter and to flow therefrom through port 158 into channels 178, 179 and 180 into conduit 23. The flow continues until the flow in this direction through the meter has caused sleeve 153 to rotate in the respective follow up direction until neutral position of the sleeve and plug 154 is once more established. It will be understood that further steering in the starboard and port directions is accomplished by turning wheel 71 in one and the other direction, and that for each movement of the wheel, a corresponding movement of the lower housing portion of the outboard leg is produced, the extent of which is directly proportional to the number of degrees of movement of the steering wheel.

A pair of safety relief valves 195 and 196 are arranged to pass oil under excessive pressure from the conduits 22 and 23 into the outlet line 170 to prevent damage to the steering cylinder assembly.

A three way manually operated selector valve 197 is connected to outlet line 170 from the steering sub-system. In a valve position 2, with the valve plug 198 rotated about 30 counterclockwise from the position 3 in which the valve is shown in FIG. 6, line 170 is connected to sump return line 199. In order to originally fill the steering system with oil and to bleed entrapped air from the steering cylinders and from space 78 (shown in FIGS. 1 and 4), the valve 197 is preferably set in position 2 and the steering wheel is turned to port to and beyond the point at which piston 66 has moved fully into cylinder 67 thereby to cause oil to flow through port 82 in piston 64. The wheel is then turned to starboard until the limit position of the pistons is reached and upon continued starboard steering oil is caused to flow through port 86 in piston 66. This operation is repeated as may be necessary to eliminate trapped air.

The elements of the trimming and tilting sub-system as described in connection with FIGS. 2 and 3 are shown diagrammatically or schematically in FIG. 6, together with further parts of the hydraulic system.

There are two identical interconnected trimming and tilting cylinder assemblies 18 and 18', one for each side of the cente'rline of the drive unit. It will be understood that the following description with respect to assembly 18 is equally applicable to the parallel connected assembly 18'.

Valve 197 is conveniently located at the helmsman station in the boat with operating handle 201 readily accessible.

With valve 197 in position 2, the pump up or inner end chamber 200 of cylinder 116 is closed off by the valve plug 198 which seals conduit 138. A pressure relief valve 202 is, however, connected to permit bypassing of oil under excessive pressure in conduits 138, 139 into oil return line 199. With valve 197 in position 3," pressure oil from line 170, which serves as the oil outlet line from the hydraulic steering arrangement and the pressure oil supply line for the tilting and trimming sub-system, is introduced into conduit 139, preferably through a restriction 203, into the pump up chamber 200 of cylinder 116, and of course, into the corresponding chamber of the cylinder assembly 18. Such supplying of pressure oil causes extension of piston rod 118 and rearward tilting of the outboard leg. The resultant movement of piston 115 forces oil into conduit 124 and thence through normally open reverse lock valve 135 and relief valve 131 into conduits 129 and 138. The volume of oil flowing into chamber 200 will be greater than the volume flowing out of the outer end 119 of the cylinder through conduit 124 because of the volume taken up by the piston rod in the cylinder.

If the leg is prevented from tilting by external force applied thereto, for example, if the leg has reached its maximum tilt position, while valve 197 is in position 1, oil will be bypassed from conduit 139 through pressure relief valve 202 to the sump. Relief valve 202 is, however, more heavily spring loaded than valve 127, and if the reverse lock valve 135 is closed while valve 197 is set in position 1 to cause tilting, oil will pass through relief valve 127, while tilting movement of the leg continues. Now if further tilting is prevented by an external force on the leg, valve 202 would again open.

When valve 197 is in position 3, as shown in full lines in FIG. 6, the leg is free to move forwardly, toward a position of less tilt, with oil freely flowing through check valve 136 and into the cylinder 116 through conduit 124 and with oil flowing from chamber 200 through valve 197 and into sump 72.

Normally valve 197 will remain in position 2, with conduit 139 sealed, except when the trim or tilt position of the leg is being adjusted. When the engine is shifted into reverse, reverse lock valve 135 is operated by handle 20 into a position to close conduit 133. As heretofore explained, valve 135 is not designed to close off the passage from conduit 124 to check valve 136, but check valve 136 does not permit oil to flow in a direction from cylinder connection 124 through valve 135 to the sump but only from the sump to the cylinder. With valve 131 now isolated by closing of valve 135, full reverse power may be applied without opening pressure relief valve 127.

At any time that the outboard leg is forced to tilt, such as by striking bottom or a submerged or floating object during forward movement of the boat, assuming valve 197 to be in position 2, oil will be forced through relief valve 131, with make-up oil as required to fill chamber 200 being supplied through check valve 136 from the sump return line 199, which may be supplied from oil passing from line 170 through valve 197 or from the sump itself. If the reverse lock valve is in closed position when the leg is forced to tilt, oil would be forced through relief valve 127, although it would be unusual for the reverse lock valve to be closed with the engine in reverse at a time when there would be sufficient forward motion of the boat to cause such kicking up of the leg.

Restriction 203 is proportioned to restrict the speed of tilting-up of the outboard leg when valve 197 is placed in position 1 to such tilting speed as may be found desirable. The trim of the outboard leg may be adjusted by moving valve 197 to position 1 to adjust the leg rearwardly or to position 3 to adjust the leg forwardly, the valve being then set in position 2 to maintain the leg in its adjusted trim position.

While the invention has been described with respect to a certain specific embodiment, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.

What is claimed as new and what it is desired to secure by Letters Patent of the United States is:

1. In a boat drive unit including a steerable and tiltable outboard power leg, a mounting member for said leg fixed to the boat, said leg comprising a propeller housing including an underwater portion provided with a propeller, a support member and means supportedly connecting said propeller housing to said support member for rotation of said housing on a generally upright steering axis, means supportedly connecting said support member to said mounting member for tilting of said leg on a generally horizontal tilt axis in a rearward direction of increasing tilt angle and in a forward direction of decreasing tilt angle, a hydraulic control system for said leg comprising, a hydraulic expansible chamber device spanning said tilt axis and operatively connected between said mounting member and said support member, a steering cylinder assembly comprising a cylinder fixed to said support member and double acting piston means disposed in said cylinder, means operatively coupling said piston means to said propeller housing offset from said steering axis, a source of hydraulic liquid under pressure, a sump for supplying liquid to said source, steering control means connecting between said source and said cylinder assembly including a valve and an outlet conduit, said valve having a rest position in which said source is connected to said outlet conduit, a port steering position in which said source is connected into one of said chambers and said outlet conduit is connected to the other of said chambers, and a starboard steering position in which said source is connected into said other chamber and said outlet conduit is connected to said one chamber, a three way manually controlled valve connected to said conduit to receive pressure liquid therefrom and in a first position of said three way valve to supply said fluid to a pump-up side of said expansible chamber device to power tilt said leg in said rearward direction, in a second position to seal off said side thereby to restrain said leg against forward tilting and to connect said conduit to said sump, and in its third position to connect said side and said conduit to said sump thereby to release said leg for forward movement on said axis.

2. In a boat drive unit including a steerable and tiltable outboard leg, a mounting member for said leg fixed to the boat, said leg comprising a propeller housing including an underwater portion provided with a propeller, a support member and means supportedly connecting said propeller housing to said support member for rotation of said housing on a generally upright steering axis, means supportedly connecting said support member to said mounting member for tilting of said leg on a generally horizontal tilt axis in a rearward direction of increasing tilt angle and in a forward direction of decreasing tilt angle, a hydraulic control system for said leg comprising, a hydraulic expansible chamber device spanning said tilt axis and operatively connected between said mounting member and said support member and adapted to tilt said leg upon the supplying of hydraulic fluid under pressure thereto, double acting hydraulic cylinder and piston means operatively coupled between said support member and said propeller housing, said last means including two conduits and operative upon supply of pressure liquid into one of said conduits to swing said propeller housing to port and to supply pressure liquid through said other conduit, and upon supply of pressure liquid into said other conduit to swing said propeller housing to starboard and to supply pressure liquid through said one conduit, a hydraulic liquid sump, a hydraulic pressure pump connected to said sump, a fluid return line connected into said sump, steering control valve means connected to said pump, to said conduits and to said return line, said valve means being operative selectively (l) to supply pressure liquid from said pump to said one conduit and to connect said other conduit to said return line, (2) to supply pressure liquid to said other conduit and to connect said one conduit to said return line, and (3) to seal said conduits and to supply pressure liquid from said pump to said return line thereby to fix said propeller housing with respect to said support member, and a tilt control valve interposed in said return line operable into selective positions (1) to divert pressure liquid therefrom into said expansible chamber device thereby to tilt said leg, (2) to seal off said device thereby to retain the leg in its position of tilt, and (3) to connect said device to said sump thereby to reduce the tilt angle of said leg.

3. In a marine propulsion mechanism, the combination with mounting bracket means adapted to be secured to a boat and a propulsion unit pivotally connected to the mounting bracket means on a horizontal transverse axis to provide for tilt movement of the unit in a generally vertical plane, an extensible power tilt unit comprising a double acting hydraulic liquid filled cylinder having a piston therein dividing said cylinder into first and second enclosed chambers, a piston rod connected to said cylinder through said second chamber thereof, said tilt unit being connected between said bracket means and said propulsion unit spanning and below said axis thereby to tilt up said propulsion unit upon extension thereof and to be extended upon tilting up of said propulsion unit from the imposition of an external force thereto, a pressure relief valve having a predetermined operating pressure connected from said first chamber to said second chamber, means including a control valve, a liquid sump and a pump to supply hydraulic liquid from said sump under pressure from the pump outlet, a shut off valve disposed between said second chamber and said pressure relief valve, a second pressure relief valve operative at a pressure substantially greater than the operative pressure of said first relief valve connected from said second chamber to said first chamber, said control valve having a first position connecting the outlet of said pump to supply pressure liquid to said first chamber, a second position to seal off said first chamber thereby to restrain said unit against contraction and to connect said pump outlet to said sump, and a third position connecting said first chamber and said pump outlet to said sump, and a check valve connected from said sump to said shut off valve oriented to pass hydraulic liquid from said sump to said second chamber through said shut off valve when the shut off valve is open and when said piston is moving in a direction to increase the volume of said second cylinder.

4. 'A trimming and tilting system for a boat outboard power leg including a fixed mounting member and a leg support member connected thereto by means establishing a horizontal tilt axis for the leg, said system being of the type comprising an extensible cylinder and piston assembly connected between said members spanning said axis, a hydraulic liquid sump and a pump connected to said means for supplying hydraulic liquid under pressure, said system being characterized in said assembly including a rod connected to said piston and extending through one end of said cylinder and occupying a substantial volume in said cylinder between said piston and said end, a

pressure relief valve, a reverse lock valve, res ctive conduits connecting said relief valve to said one and t e other ends of said cylinder, said relief valve being oriented to pass liquid under pressure from said one to the other of said ends, said lock valve being connected in one of said conduits and having an open position to permit flow of liquid through said relief valve and a closed position to prevent such flow, a check valve connected between said sump and said one end of said cylinder and oriented to pass liquid from said sump to said one end and to prevent passage of liquid from said one end into said sump, manually operable valve means, respective conduit connections from said valve means to said sump, to said other end and to said pump, said valve means having a first position opening said connection from said other end to said pump connection whereby said pump supplies liquid under pressure into said other end, a second position sealing said other end connection, and a third position opening said other end connection into said sump connection.

5. In a boat drive unit including an outboard leg comprising an upper housing portion and a steerable lower propeller housing portion rotatably mounted on said upper portion for rotation on a generally upright steering axis, hydraulic cylinder means, unitary piston means in said cylinder means, said cylinder means having closed ends and said piston means being double acting therein, said cylinder means and piston means being operatively connected between said housing portions for steering movement of said lower portion on said axis in response to movement of said piston means with respect to said cylinder means, said piston means being provided with a port normally closed by a wall portion of said cylinder means and opened upon maximum movement of the piston means outwardly of one end chamber of said cylinder means, and conduit means in said piston means extending from said port and connecting said one end chamber into the other end chamber of said cylinder means when said port is open, a liquid sump, a hydraulic pump connected to said sump, and valve means connected to said pump and to said sump for selectively supplying liquid under pressure from said pump into said one and said other end chambers of said cylinder means and for concurrently connecting the respectively opposite end chamber into said sump.

6. The combination according to claim 5 wherein said valve means comprises a pair of relatively movable members provided with registering ports and liquid conduits, said members having a neutral first relative position in which said source is connected to said sump and said chambers are sealed off, a port steering second relative position in which said members are displaced in one direction from said neutral relative position and in which said one end chamber is connected to said source and said other end chamber is connected to said sump, and a starboard steering third relative position in which said members are displaced in the respectively opposite direction from said neutral relative position and in which said other end chamber is conndcted to said source and said one end chamber is connected to said sump, manually operative means for displacing one of said members from said neutral position selectively in said directions, and means operated by liquid flow through said valve means to move the other of said members in a follow-up direction in response to displacement of said members from said neutral position.

7. The combination according to claim 5 wherein said conduit means is provided with a check valve oriented to block liquid flow from said other end chamber into said one end chamber.

8. The combination according to claim 5 wherein said valve means comprises a pair of relatively movable valve members for cooperatively controlling the flow to and from said end chambers and having a neutral position, one of said members being manually movable, and means responsive to said flow for moving said other member in a follow-up direction. 

1. In a boat drive unit including a steerable and tiltable outboard power leg, a mounting member for said leg fixed to the boat, said leg comprising a propeller housing including an underwater portion provided with a propeller, a support member and means supportedly connecting said propeller housing to said support member for rotation of said housing on a generally upright steering axis, means supportedly connecting said support member to said mounting member for tilting of said leg on a generally horizontal tilt axis in a rearward direction of increasing tilt angle and in a forward direction of decreasing tilt angle, a hydraulic control system for said leg comprising, a hydraulic expansible chamber device spanning said tilt axis and operatively connected between said mounting member and said support member, a steering cylinder assembly comprising a cylinder fixed to said support member and double acting piston means disposed in said cylinder, means operatively coupling said piston means to said propeller housing offset from said steering axis, a source of hydraulic liquid under pressure, a sump for supplying liquid to said source, steering control means connecting between said source and said cylinder assembly including a valve and an outlet conduit, said valve having a rest position in which said source is connected to said outlet conduit, a port steering position in which said source is connected into one of said chambers and said outlet conduit is connected to the other of said chambers, and a starboard steering position in which said source is connected into said other chamber and said outlet conduit is connected to said one chamber, a three way manually controlled valve connected to said conduit to receive pressure liquid therefrom and in a first position of said three way valve to supply said fluid to a pump-up side of said expansible chamber device to power tilt said leg in said rearward direction, in a second position to seal off said side thereby to restrain said leg against forward tilting and to connect said conduit to said sump, and in its third position to connect said side and said conduit to said sump thereby to release said leg for forward movement on said axis.
 2. In a boat drive unit including a steerable and tiltable outboard leg, a mounting member for said leg fixed to the boat, said leg comprising a propeller housing including an underwater portion provided with a propeller, a support member and means supportedly connecting said propeller housing to said support member for rotation of said housing on a generally upright steering axis, means supportedly connecting said support member to said mounting member for tilting of said leg on a generally horizontal tilt axis in a rearward direction of increasing tilt angle and in a forward direction of decreasing tilt angle, a hydraulic control system for said leg comprising, a hydraulic expansible chamber device spanning said tilt axis and operatively connected between said mounting member and said support member and adapted to tilt said leg upon the supplying of hydraulic fluid under pressure thereto, double acting hydraulic cylindeR and piston means operatively coupled between said support member and said propeller housing, said last means including two conduits and operative upon supply of pressure liquid into one of said conduits to swing said propeller housing to port and to supply pressure liquid through said other conduit, and upon supply of pressure liquid into said other conduit to swing said propeller housing to starboard and to supply pressure liquid through said one conduit, a hydraulic liquid sump, a hydraulic pressure pump connected to said sump, a fluid return line connected into said sump, steering control valve means connected to said pump, to said conduits and to said return line, said valve means being operative selectively (1) to supply pressure liquid from said pump to said one conduit and to connect said other conduit to said return line, (2) to supply pressure liquid to said other conduit and to connect said one conduit to said return line, and (3) to seal said conduits and to supply pressure liquid from said pump to said return line thereby to fix said propeller housing with respect to said support member, and a tilt control valve interposed in said return line operable into selective positions (1) to divert pressure liquid therefrom into said expansible chamber device thereby to tilt said leg, (2) to seal off said device thereby to retain the leg in its position of tilt, and (3) to connect said device to said sump thereby to reduce the tilt angle of said leg.
 3. In a marine propulsion mechanism, the combination with mounting bracket means adapted to be secured to a boat and a propulsion unit pivotally connected to the mounting bracket means on a horizontal transverse axis to provide for tilt movement of the unit in a generally vertical plane, an extensible power tilt unit comprising a double acting hydraulic liquid filled cylinder having a piston therein dividing said cylinder into first and second enclosed chambers, a piston rod connected to said cylinder through said second chamber thereof, said tilt unit being connected between said bracket means and said propulsion unit spanning and below said axis thereby to tilt up said propulsion unit upon extension thereof and to be extended upon tilting up of said propulsion unit from the imposition of an external force thereto, a pressure relief valve having a predetermined operating pressure connected from said first chamber to said second chamber, means including a control valve, a liquid sump and a pump to supply hydraulic liquid from said sump under pressure from the pump outlet, a shut off valve disposed between said second chamber and said pressure relief valve, a second pressure relief valve operative at a pressure substantially greater than the operative pressure of said first relief valve connected from said second chamber to said first chamber, said control valve having a first position connecting the outlet of said pump to supply pressure liquid to said first chamber, a second position to seal off said first chamber thereby to restrain said unit against contraction and to connect said pump outlet to said sump, and a third position connecting said first chamber and said pump outlet to said sump, and a check valve connected from said sump to said shut off valve oriented to pass hydraulic liquid from said sump to said second chamber through said shut off valve when the shut off valve is open and when said piston is moving in a direction to increase the volume of said second cylinder.
 4. A trimming and tilting system for a boat outboard power leg including a fixed mounting member and a leg support member connected thereto by means establishing a horizontal tilt axis for the leg, said system being of the type comprising an extensible cylinder and piston assembly connected between said members spanning said axis, a hydraulic liquid sump and a pump connected to said means for supplying hydraulic liquid under pressure, said system being characterized in said assembly including a rod connecteD to said piston and extending through one end of said cylinder and occupying a substantial volume in said cylinder between said piston and said end, a pressure relief valve, a reverse lock valve, respective conduits connecting said relief valve to said one and the other ends of said cylinder, said relief valve being oriented to pass liquid under pressure from said one to the other of said ends, said lock valve being connected in one of said conduits and having an open position to permit flow of liquid through said relief valve and a closed position to prevent such flow, a check valve connected between said sump and said one end of said cylinder and oriented to pass liquid from said sump to said one end and to prevent passage of liquid from said one end into said sump, manually operable valve means, respective conduit connections from said valve means to said sump, to said other end and to said pump, said valve means having a first position opening said connection from said other end to said pump connection whereby said pump supplies liquid under pressure into said other end, a second position sealing said other end connection, and a third position opening said other end connection into said sump connection.
 5. In a boat drive unit including an outboard leg comprising an upper housing portion and a steerable lower propeller housing portion rotatably mounted on said upper portion for rotation on a generally upright steering axis, hydraulic cylinder means, unitary piston means in said cylinder means, said cylinder means having closed ends and said piston means being double acting therein, said cylinder means and piston means being operatively connected between said housing portions for steering movement of said lower portion on said axis in response to movement of said piston means with respect to said cylinder means, said piston means being provided with a port normally closed by a wall portion of said cylinder means and opened upon maximum movement of the piston means outwardly of one end chamber of said cylinder means, and conduit means in said piston means extending from said port and connecting said one end chamber into the other end chamber of said cylinder means when said port is open, a liquid sump, a hydraulic pump connected to said sump, and valve means connected to said pump and to said sump for selectively supplying liquid under pressure from said pump into said one and said other end chambers of said cylinder means and for concurrently connecting the respectively opposite end chamber into said sump.
 6. The combination according to claim 5 wherein said valve means comprises a pair of relatively movable members provided with registering ports and liquid conduits, said members having a neutral first relative position in which said source is connected to said sump and said chambers are sealed off, a port steering second relative position in which said members are displaced in one direction from said neutral relative position and in which said one end chamber is connected to said source and said other end chamber is connected to said sump, and a starboard steering third relative position in which said members are displaced in the respectively opposite direction from said neutral relative position and in which said other end chamber is conndcted to said source and said one end chamber is connected to said sump, manually operative means for displacing one of said members from said neutral position selectively in said directions, and means operated by liquid flow through said valve means to move the other of said members in a follow-up direction in response to displacement of said members from said neutral position.
 7. The combination according to claim 5 wherein said conduit means is provided with a check valve oriented to block liquid flow from said other end chamber into said one end chamber.
 8. The combination according to claim 5 wherein said valve means comprises a pair of relatively movable valve members for cooperatively controlling the flow to and from said End chambers and having a neutral position, one of said members being manually movable, and means responsive to said flow for moving said other member in a follow-up direction. 